A conventional dishwasher for washing eating utensils is described with reference to FIG. 43. The conventional dishwasher comprises body 1, washing tub 2, cover 3, exhaust port 4, rack 5, washing pump 8, washing nozzle 9, drain pump 10, controller 11, feed water hose 12, drain hose 13, heater 14, fan 15, and water level detecting device 20. Cover 3 is used for opening or closing an opening of the washing tub, and has exhaust port 4. Rack 5 accommodates eating utensils. Washing pump 8 pressurizes washing water. Washing nozzle 9 is disposed in a lower part of washing tub 2. Drain pump 10 discharges, from the dishwasher, washing water reserved in the washing tub. Controller 11 controls operations of washing pump 8 and drain pump 10. Heater 14 is disposed on a bottom of washing tub 2, and heats washing water, and heats air during drying. Fan 15 is used for drying. Rack 5 is supported via rollers 6 by a rail surface 7 formed on a side surface of washing tub 2. Washing nozzle 9 sprays the washing water pressurized by washing pump 8, from below to the eating utensils held by rack 5. Water level detecting device 20 detects a washing water level.
For washing eating utensils, the eating utensils to be washed are held in rack 5 of washing tub 2, a detergent is thrown in, and an operation is started. After the start of the operation, firstly a feed water process of supplying a predetermined amount of washing water to washing tub 2 is performed so as to stabilize a pressurizing operation of the washing water by washing pump 8. Washing pump 8 has centrifugal blades (not shown) and an electric motor (not shown) for driving the blades. Approximately a predetermined interval (it is hereinafter called washing water level) is maintained between intake port 16 of washing pump 8 and a washing water surface. Next, a primary washing process is performed. During the primary washing process, the washing water pressurized by washing pump 8 and heated by heater 14 is sprayed together with the detergent from spray port 17 of washing nozzle 9. The washing water is sprayed vertically, or obliquely and upwardly from spray port 17 of washing nozzle 9. Washing nozzle 9 is rotated substantially horizontally by reaction force of the spray. Collision force of the washing water sprayed from the rotating washing nozzle 9, the detergent, and heat are used for washing the eating utensils.
After the primary washing process is performed for a predetermined period, a draining process is performed. During the draining process, the washing water containing dirt removed from the eating utensils is discharged from the dishwasher by drain pump 10. Subsequently, a feed water process of supplying new washing water, a rinsing process of spraying the washing water from washing nozzle 9 to rinse the eating utensils soiled with the detergent or garbage (dirt attached to the eating utensils), and the draining process are sequentially repeated four times. These processes constitute a washing procedure.
After the washing procedure, a drying process is performed. During the drying process, fan 15 feeds air into washing tub 2 from outside of the dishwasher. The air is fed from blast duct 18 into washing tub 2 through blast port 19, and simultaneously heater 14 is intermittently operated, thereby generating warm air. This warm air vaporizes water drops attached to the eating utensils to dry the eating utensils. During the drying process, highly humid air in washing tub 2 is exhausted from the dishwasher through exhaust port 4.
However, the washing nozzle of the conventional dishwasher sprays the washing water to various shapes of eating utensils used in a typical home only from a constant direction. Sufficient washing performance therefore cannot be obtained. When the washing water is not sprayed from an upper part of the washing tub during washing of an eating utensil such as a teacup or a soup bowl having a rim at its bottom, small garbage is apt to accumulate on the rim and water for rinsing does not disperse sufficiently. Therefore, rinsing is insufficient. For addressing these problems, a method of spraying washing water from various directions using a plurality of washing nozzles is proposed in Japanese Patent Application Non-examined Publication No. H5-305050. In this method, water to be reserved in a washing tub must be increased, relative to that associated with the conventional dish washer, for spraying water from the plurality of nozzles at the same time.
The increase of the fed water results in a longer time being required to raise temperature of the washing water. This method therefore requires a longer operation time, more electricity, more usage of water, and a large washing pump. This causes various problems such as increase of cost and increase of noise or vibration due to the spray of much washing water at the same time.
Japanese Patent Application Non-examined Publication No. H5-176875 proposes a method for addressing these problems using a plurality of washing pumps. In this method, however, a plurality of washing pumps must be disposed for respective washing nozzles, and therefore volume ratio of a washing mechanism to an entire dishwasher increases. A space required for washing eating utensils cannot be sufficiently prepared, or size of the dishwasher body increases more than necessary. Japanese Patent Application Non-examined Publication No. H5-176875 has these problems.
Additionally, Japanese Patent Application Non-examined Publication No. H6-30853 discloses a washer having a structure in which a three-way valve is heavily used for water division. However, when this washer is used as a dishwasher that treats washing water containing garbage or foreign matter, operational reliability of the valve cannot be ensured. As a number of diversion channels increases, a number of three-way valves increases. The washer cannot deal with a complex discharge behavior of washing water of each washing nozzle, a specific abnormal sound occurs during a valving operation, and cost increases. Japanese Patent Application Non-examined Publication No. H6-30853 has these problems.
As other examples of a washer spraying washing water, there are a component washer for removing grease or chips from a component machined by a machine tool or the like, and a vegetable washer for removing foreign matter or chemicals attached to vegetables. However, these washers have the problems discussed above.